The present invention relates to a liquid crystal display device, in particular, a transflective liquid crystal display device and a manufacturing method thereof.
Japanese Patent Laid-Open Publication No. 2005-338256 (corresponding to US 2005/0264731 A1; hereinafter, referred to as Patent Document 1) describes a transflective in-plane switching (IPS) liquid crystal display device which applies a lateral electric field to a liquid crystal layer. Not only the transflective liquid crystal display device which employs the IPS system but also the device which employs, for example, a twisted nematic (TN) system or a vertical alignment (VA) system, includes a transmissive display part and a reflective display part in one pixel. The reflective display part of the transflective liquid crystal display device exemplified in Patent Document 1 includes an embedded retardation plate whose retardation is equal to a half wavelength. Further, retardation of a liquid crystal layer in the reflective display part is adjusted to a quarter wavelength in the transflective liquid crystal display device to enable a reflective display under a wide range of environments including well-lit places and dark places, as well as transmissive display of high quality at a wide viewing angle. The embedded retardation plate is formed of molecules exhibiting a birefringence such as liquid crystal molecules.
Such a liquid crystal display device has the following structure. On a color filter-side substrate, RGB resist layers, a leveling layer for planarizing the RGB resist layers, an alignment film for aligning molecules of an embedded retardation plate, the embedded retardation plate formed of molecules aligned by the alignment film, and an alignment film for aligning molecules in the liquid crystal layer are deposited in this order.
Therefore, a manufacturing process of the liquid crystal display device requires a step of applying and baking, for example, a polyimide-based organic material, and then performing an alignment process on the baked polyimide-based organic material by a rubbing method to form the alignment film for aligning the molecules in the embedded retardation plate.